bread and butter=your main source of income, or the most important issue (维持生活所需的), Health and education are the bread and butter issues facing the UK government.
wheel and deal=to make deals in a skillful and perhaps dishonest way when buying and selling things (讨价还价,玩弄手段,投机取巧), If you need a new car, try speaking to John. He's a bit of a wheeler and dealer.